There are a wide range of lifting and/or hoisting devices used in the industry which include, but are not limited, to center-pull style hoist rings. These devices are used to lift a variety of heavy loads or objects, such as die sets and molds. However, while the invention has been found to work particularly well with these center-pull hoist rings wherein it is being described below in connection with center-pull hoist rings, the invention has broader applications and may be used for a variety of applications where it is necessary to monitor, record and communicate applied loads over the service life of the device. These applications can include the use of a hoist ring used to lift structures such as containers, aircrafts, vehicles, boats, equipment, dies, tooling, molds, rigging, windmills, etc.
Through the years, a large number of hoisting devices have been developed which allow for a ring to be connected to the hook of a hoist wherein the ring pivots and/or swivels for the purpose of automatically adjusting the disposition of the ring with respect to the force being applied to the hoist during the lifting procedure. Such devices are found in patents incorporated by reference herein which will be discussed more below.
The center-pull hoist devices have a post assembly that allows 360-degree rotation of a support or body member. The rotating support member carries the load lifting ring, which can be in many forms include the form of a U-shaped clevis or bail. The clevis can pivot about a center clevis axis of the rotating support member and has a pivot arc of about 180 degree (bail angle).
Like the center-pull style, the side-pull hoist ring includes a rotating support member mounted onto the load by a post assembly. In a side-pull hoist ring, the support member can be generally U-shaped to define an outer bite portion in which a circular load ring is pivotally mounted. The circular load ring is offset from the axis of the center post assembly.
These prior patents include the device shown in Schron Jr. et al U.S. Pat. No. 5,634,734 that discloses a center-pull style hoist device and is incorporated by reference for showing the same. Also incorporated by reference are the Ma U.S. Pat. No. 6,749,237, the Tsui U.S. Pat. Nos. 5,405,210 and 5,848,815, the Sawyer et al U.S. Pat. No. 5,586,801, and the Chandler U.S. Pat. No. 5,352,056 that all show different styles of center-pull hoist ring.
Fuller et al U.S. Pat. No. 6,652,012; Fuller et al U.S. Pat. No. 6,443,514; and Fuller et al U.S. Pat. No. 6,068,310 all disclose side-pull hoisting devices and are incorporated by reference for showing the same.
All of these device disclose effective hoisting devices that have been used effectively in the industry for many years and which are provided as background for the invention of this application.
In addition to the above-described hoisting devices, also known in the patent art is a patent to Mueller U.S. Pat. Nos. 5,286,130, and 3,492,033 which disclose a clevis hoist ring assembly. The Mueller patents are incorporated by reference for showing yet another style of hoist ring that could utilize with the invention of this application
However, while hoist rings are designed to be very robust, every hoist ring has a predetermined load limit based on the size and design of the ring. And, if a predetermined load limit is exceeded, the ring can be damaged. Thus, when a hoist ring is utilized to lift or support a critical load, it is important to know whether the ring has been damaged by its use on prior loads. Therefore, when dealing with critical loads, hoist rings are often pulled out of service to test the rings to ensure that there has been no damage to the ring during prior use. As can be appreciated, this can be costly and can remove the ring from service for an extended amount of time over its service life. This is especially true if there is no data on the prior use. Therefore, the service intervals of existing hoist rings must be set based on the worst case scenarios instead of the actual use of the ring. However, if the service life of the ring could be monitored, both the service life of the ring could be extended and the service intervals could be determined based on the actual use of each ring individually thereby minimizing the amount of time the ring is out of service throughout its service life. Therefore, there is a need for a hoist ring that can monitor its own use and store data associated with this use such that service intervals can be based on actual use of each hoist ring.